1. Field of the Invention
The invention relates to solvents for softening, loosening, or removing cured fiberglass resin and cured flexible or rigid urethane foams from tools, processing equipment and other substrates.
2. Description of Related Methods
A variety of solvents have been used to flush urethane processing equipment and clean metal parts and tools after urethane foam has cured on them. Some of the solvents used include such compounds as dimethyl formamide, 1,1,1-trichloroethane, methylene chloride, chlorofluorocarbons, toluene, xylene, acetone, methyl ethyl ketone, ethylene glycol ethers, tetrahydrofuran, and .gamma.-butyrolactone. However, though these compounds are effective solvents, the use of each presents a hazard or complication of one type or another. For example, the chlorine-containing compounds are now thought to contribute to ozone depletion in the atmosphere. The other solvents are either toxic, suspected carcinogens, or very volatile, and thus present health and safety problems. An alternative solvent, n-methyl pyrrolidone, is more easily handled, and presents fewer environmental problems, but is expensive. Thus, it would be a substantial improvement in the art if a relatively inexpensive yet effective solvent formulation were available to remove cured rigid and flexible urethane foams, and that did not present the environmental, health and safety problems of the prior art solvent formulations.
Acetone, methyl ethyl ketone, and diacetone alcohol are the solvents most commonly used to remove cured polyester resin (fiberglass) from machine parts and tools. However, acetone and methyl ethyl ketone are not favored because of safety hazards resulting from their high volatilities and low flash points. Diacetone alcohol is very polar, and therefore presents other problems when used alone. Thus, it also would be a substantial improvement in the art if a solvent formulation were available that was effective for removing polyester resin, yet did not present the problems associated with the prior art solvents mentioned above.
Applicants have discovered, surprisingly, that a co-solvent system comprising an alkylene carbonate and tetramethyl urea will dissolve cured polyester resins and cured rigid or flexible polyurethane foams. Additionally, the co-solvent system of the present invention avoids many of the health, safety and environmental problems associated with the prior art solvents, and is economically attractive as well.